Answer:
Oxygen Gas
Step-by-step explanation:
The balanced equation shows us the reactant ratio of the reaction.
This means that for every one mole of CH3CH2OH, we need 3 moles of O2 to react with it. Because we need more O2, (3x as much) than ethanol and we have the same given amount (1 mole of each), the oxygen will be the limiting reagent. (1 mole of oxygen would only require 1/3 moles of ethanol to react).
Hope this helped!